nix: set CMake version to 3.30.4

.gitignore

@@ -0,0 +1 @@
+out/

CMakeLists.txt

@@ -1,11 +1,17 @@
 cmake_minimum_required(VERSION 3.28)
-project(ModulesHelloWorld CXX)
 
-set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_EXTENSIONS ON)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
-add_library(lib)
-target_sources(lib PUBLIC FILE_SET CXX_MODULES FILES lib.cxx)
+# enable modules support
+set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
 
-add_executable(hellomodules main.cxx)
-target_link_libraries(hellomodules lib)
+project(gooey LANGUAGES CXX)
+
+set(CMAKE_CXX_MODULE_STD ON)
+
+add_subdirectory(game)
+
+add_executable(gooey src/main.cxx)
+target_link_libraries(gooey game)

flake.nix

@@ -11,7 +11,8 @@
   }:
     flake-utils.lib.eachDefaultSystem (system: let
       pkgs = nixpkgs.legacyPackages.${system};
-      inherit (pkgs.llvmPackages_19) stdenv;
+      stdenv = pkgs.llvmPackages_19.libcxxStdenv;
+      cmake-version = "3.30.4";
 
       gooey = stdenv.mkDerivation {
         pname = "gooey";
@@ -19,10 +20,18 @@
         # inherit system;
 
         src = ./.;
-        buildInputs = [
-          pkgs.cmake
+        nativeBuildInputs = [
+          (pkgs.cmake.overrideAttrs {
+            version = "3.30.4";
+            src = pkgs.fetchurl {
+              url = "https://cmake.org/files/v${pkgs.lib.versions.majorMinor cmake-version}/cmake-${cmake-version}.tar.gz";
+              hash = "sha256-x1nJcnTx56qq/LHw0mH53pvzpdbst+LfYWMkpG/nBLI=";
+            };
+          })
           pkgs.ninja
+        ];
 
+        buildInputs = [
           (pkgs.callPackage ./nix/SDL3.nix {})
           pkgs.llvmPackages_19.clang-tools
         ];
@@ -42,7 +51,7 @@
       };
     in {
       packages.default = gooey;
-      devShells.default = pkgs.mkShell {
+      devShells.default = pkgs.mkShell.override {inherit stdenv;} {
         name = "gooey";
         inputsFrom = [gooey];
         CMAKE_GENERATOR = "Ninja";

game/CMakeLists.txt

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 3.28)
+
+add_library(game)
+target_sources(game PUBLIC FILE_SET CXX_MODULES FILES src/game.cxx)

game/src/game.cxx

@@ -1,8 +1,9 @@
 // Global module fragment, where #includes can happen
 module;
-#include <iostream>
 
-export module lib;
+import std;
+
+export module game;
 
 export class lib
 {
@@ -17,5 +18,5 @@ lib::~lib() = default;
 
 void lib::helloworld()
 {
-    std::cout << "Hello world!" << std::endl;
+    std::print("Hello world!\n");
 }

src/main.cxx

@@ -1,4 +1,4 @@
-import lib;
+import game;
 
 int main()
 {